interview next week

I'm an emt-b and am in school for my intermediate, I've never done fire before but i want to oh so bad! i have an interview next week but i was wondering if someone could please tell me what to expect..? what to wear? I usually wear a skirt and heels to an interview but i want them to take me serious, so nice dress pants and flats? also, what kind of questions do they ask? how can i show them i can do this job without being too cocky? any help would be greatly appreciated!